Comorbidity does not impact risk of prostate cancer death

A large observational study published in the Journal of Clinical Oncology showed that comorbidity in patients with prostate cancer (PCa) affects other cause-mortality, but it does not affect the risk of dying from PCa, regardless of treatment.

Lead author Prabhakar Rajan, PhD, FRCS(Urol), from the Queen Mary University of London, and colleagues suggested that this information could be helpful when counseling PCa patients with comorbidity about treatment options. Patients with comorbidity that pose a greater risk of mortality than the risk of death from PCa may opt to withhold treatment to limit PCa treatment-related morbidity without compromising outcome.

The study used the Prostate Cancer Database Sweden (PCBaSe), a composite population-based data set that links nine national registers in Sweden and captured more than 98% of all PCa cases since 1998. The database provides extensive information about patient demographics and tumor characteristics, as well as treatments.

A total of 118,543 men who were diagnosed with PCa were included in the study and followed until death from PCa or other causes. The median follow-up was 8.3 years, with a maximum of 16 years.

Patients were categorized by patient characteristics such as marital status and educational level, tumor characteristics including serum prostate-specific antigen (PSA), tumor grade and clinical stage, as well as by treatment type—radical prostatectomy (RP), radical radiotherapy (RT), watchful waiting (WW), and androgen deprivation therapy. Data were stratified by Charlson comorbidity index (CCI), a scoring system that estimates the burden of concomitant disease ranging from 0 (no comorbidity) to ≥3 (severe comorbidity) (See table below).

At the time of diagnosis, patients with greater morbidity were generally older and had higher median PSA than those with no comorbidity. Furthermore, men without comorbidity had a higher proportion of low-grade, localized tumors. Therefore, the proportion of men treated with radical therapies (RP or RT) was greater than in men with little or no comorbidity.

CCI score and deaths by end of study

CCI Score	N	PCa-related death	Death from other causes
0	87,816	15,403	15,203
1	16,186	3,591	5,409
2	9,114	1,895	3,683
3	5,427	1,134	2,849

In the unadjusted data set, there was an effect of increased comorbidity on both PCa-specific and other-cause mortality. For patients with a CCI score ≥3 compared with no comorbidity, the hazard ratio (HR) for PCa-specific mortality was 1.99; for other-cause mortality the HR was 5.62.

After adjusting for patient and tumor characteristics, the effect of limited comorbidity (CCI score of 1 or 2) on PCa-specific mortality was not statistically significant, but was maintained for other-cause mortality across all CCI groups.

Similarly, after adjusting for treatment type, the association between comorbidity and PCa-specific mortality was attenuated with no clear trends across CCI groups, while the effect of increasing comorbidity on other-cause mortality was maintained.

Congestive heart failure and dementia were the only comorbidities that affected PCa-specific mortality after adjusting for patient and tumor characteristics and treatment type.

Although the study included a large data set with extensive patient and clinical information, the authors noted that it could have some limitations. Confounders may have been unmeasured or misclassified, which could result in bias.

Furthermore, the PCa- and other cause-specific survival analyses may be biased if patients who died early from other causes had a different risk of death from PCa compared to those who survived longer.

“Our findings suggest that, after adjusting for patient and tumor characteristics, comorbidity does not seem to significantly impact the risk of dying from PCa after radical treatment (RP or RT) or WW,” the authors wrote.

To read more about this study, click here.